The invention is directed to a micromechanical electrostatic relay having a base substrate that carries a base electrode layer and at least one base contact piece. An armature substrate is provided that lies on the base substrate and has at least one armature spring tongue that is worked free and attached at one side, and which carries an armature electrode layer and an armature contact piece at its free end. The spring tongue is bent away from the base substrate by a steady curvature in a quiescent condition, so that a wedge-shaped air gap is formed between the two electrode layers. The ;spring tongue conforms to the base substrate and the two contact pieces lie against one another in the working condition when a voltage is present between the electrode layers.
DE 42 05 029 C1 already discloses such a micromechanical relay. As set forth therein, such a relay structure can be manufactured, for example, of a crystalline semiconductor substrate, preferably silicon, whereby the spring tongue serving as the armature is formed out of the semiconductor substrate by appropriate doping and etching processes. How a uniform curvature can be produced in the spring tongue with a multilayer structure is likewise already fundamentally disclosed therein, whereby the various layers are stressed relative to one another due to their different coefficients of expansion and deposition temperatures. The curved spring tongue with its correspondingly curved armature electrode thus forms a wedge-shaped air gap relative to a planar base electrode on a planar base substrate that, for example, can likewise be composed of silicon or of glass as well. By applying a control voltage between the armature electrode of the spring tongue and the planar base electrode, the curved spring tongue rolls on the base electrode and thus forms what is referred to as a migrating wedge. The spring tongue is stretched during this rolling until the free end with the armature contact piece touches the base contact piece on the base substrate.
What accompanies this described switching event with the migrating wedge, whereby the steadily curved armature electrode rolls steadily, is that the actual closing and opening of the contact also occurs in a continuous motion. As a result, what is referred to as a creeping contacting occurs. An arc or an undesired heating of the contact pieces arises in the transition phase wherein the contact pieces only touch with a slight contacting force and, consequently, with a high contact resistance, whereby the contact surfaces are damaged. An abrupt switching event is therefore generally desired for relays, whereby the spring tongue or the armature contact piece completely strikes the base electrode or base contact piece when the response voltage is reached, and thus a defined contacting force results upon initial contact of the working contact. The analogous case , applies to the holding event when the control voltage is lowered. The opening of the contacts and thus the drop-off of the spring tongue should likewise occur as a trip event when the control voltage is lowered it crosses the holding voltage.